US7382399B1 - Omniview motionless camera orientation system - Google Patents

Abstract

A method and apparatus for capture of a spherical image is disclosed. The present invention includes at least one camera having a lens with at least a 180° field-of-view for capturing a hemispherical image. In a first embodiment, a second hemispherical image is created corresponding to a mirror image of the hemispherical image captured by the camera. In a second embodiment, two back-to-back cameras capture first and second hemispherical images, respectively. In both embodiments, a converter combines the two images along their outside edges to form a single, spherical image. Finally, the converter stores the complete spherical image for later retrieval and perspective corrected viewing.

Description

This application is a divisional of appl Ser. No. 08/863,584 filed May 27, 1997 now U.S. Pat. No. 6,002,430 which is a continuation-in-part of U.S. application Ser. No. 08/386,912 filed Feb. 8, 1995 now abandoned, which is a continuation of U.S. application Ser. No. 08/339,663 filed Nov. 14, 1994 now abandoned, which is a continuation of U.S. application Ser. No. 08/189,585 filed Jan. 31, 1994 (now U.S. Pat. No. 5,384,588), which is a continuation-in-part of U.S. application Ser. No. 08/014,508 filed Feb. 8, 1993 (now U.S. Pat. No. 5,359,363), which is a continuation-in-part of U.S. application Ser. No. 07/699,366 filed May 13, 1991 (now U.S. Pat. No. 5,185,667). This application is also a continuation-in-part of U.S. application Ser. No. 08/373,446 filed Jan. 17, 1995, which is a continuation-in-part of U.S. application Ser. No. 08/189,585 filed Jan. 31, 1994 (now U.S. Pat. No. 5,384,588).

This invention was made with Goverment support under contract NAS1-18855awarded by NASA. This Government has certain rights in this invention.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to an apparatus and method for capturing an image having a spherical field-of-view for subsequent viewing. Specifically, the present invention relates to a system involving a single camera having a lens with a field of view of at least 180° and associated method for capturing a first hemispherical image for subsequent combination into the spherical image. Alternatively, when the system comprises two cameras with such lenses mounted in a securely attached back-to-back arrangement, the system and method captures two distinct hemispherical images for subsequent combination into the spherical image. The preferred system includes a single-use, still image camera.

2. Background Art

The discussion of the background art related to the invention described herein relates to two subjects: spherical image capture and subsequent captured image transformations.

Spherical Image Capture

The goal of imaging technology is to make the observer feel as though he or she is part of the image. Prior art systems have partially accomplished this goal. Unfortunately, the ability of prior art systems to make the user feel part of the captured images are proportional to the cost of the image capture system.

Relating to inexpensive image capturing systems, camera companies have introduced disposable cameras. A disposable camera generally refers to a single-use camera that includes film, a lens, and a camera body, all in a single compact shell. The film includes either a single frame of film or multiple frames of film. After the entire roll of film has been exposed, the entire camera is returned for film developing. All the photographer receives back are the developed prints or slides. The manufacturer then recycles the parts from the returned camera, adds film, and ships the camera to a retailer for sale again. Disposable cameras come in various types including regular magnification cameras, telephoto cameras, water resistant cameras, and panoramic cameras.

Images captured by panoramic cameras provide wide angle horizontal images (left to right) but lack wide angle vertical images (up and down). Accordingly, while capturing a wide field-of-view on one plane (horizontal), the photographer loses the wide field-of-view on the other plane (vertical). Rotating the camera only alters the wide angle direction. The following example illustrates this shortcoming. Suppose a photographer desires to capture the grandeur of a dense forest from within the forest. While an image captured by a panoramic camera would include a sweeping cross section of trees (left to right), it world only include, at most, the middle portions of the nearest trees. To capture the forest floor and canopy, the photographer would have to take multiple panoramic photographs from looking almost straight down to looking straight up. The final image of the forest would then only be realized with the laborious task of manually cutting and pasting the different images together. Unfortunately, the left and right ends of the final image become distorted and cannot be easily resolved. The distortions created are similar to those encountered in map-making where one tries to represent a round earth on a flat map. Specifically, objects and relative distances near the extremes of the wide angle image become distorted. Additionally, this approach wastes film.

A slightly more complex panoramic camera employs a scanning drive mechanism which selectively exposes vertical strips of film as the camera scans from extreme to extreme. However, scanning panoramic cameras invariably introduce noise into captured images through vibrations generated from their scanning motions as well as take a relatively long period of time to capture the image.

Other wide-angle image capturing systems exist. For example, IMAX and 70 mm films provide high definition images on a large screen. However, these screens are flat. While a viewer can feel part of the scene when staring straight ahead, this feeling dissipates where the screen ends.

Another imaging system includes the OMNIMAX camera and projection system where an image was recorded and later projected on a spherical screen to produce an image 180 degrees wide, 100 degrees up from the horizon and 20 degrees below. While this system offers significant improvements over a flat screen projection system, the viewer's absorption into the displayed images is limited by the edges of the displayed image.

Another image capture and display system is U.S. Pat. No. 5,023,725 to McCutchen. McCutchen discloses a dodecahedral imaging system which breaks a sphere into 12 discrete polyhedrons. Each section has its own dedicated CCD camera. The images are captured and displayed on the walls of a hemispherical room. This system offers increased resolution through increasing the number of cameras used. However, as the number of cameras increase, the bulk of the imaging system likewise increases. Additionally, each camera has to be perfectly aligned with respect to the other cameras to adequately capture a spherical image. Using McCutcheon's system, increased resolution requires more bulk and more expense. Furthermore, the images of each camera are not integrated together. Accordingly, the system fails to account for the seams between the displayed images. While quickly moving images may mask these edge effects, the edge effects may be more noticeable with slow moving images.

Captured Image Transformations

Camera viewing systems are used in abundance for surveillance, inspection, security, and remote sensing. Remote viewing is critical, for example, for robotic manipulation tasks. Close viewing is necessary for detailed manipulation tasks while wide-angle viewing aids positioning of the robotic system to avoid collisions with the work space. Most of these systems use either a fixed-mount camera with a limited viewing field to reduce distortion, or they utilize mechanical pan-and-tilt platforms and mechanized zoom lenses to orient the camera and magnify its image. In the application where orientation of the camera and magnification of its image are required, the mechanical solution is large in size and can subtend a significant volume making the viewing system difficult to conceal or use in close quarters. Several cameras are usually necessary to provide wide-angle viewing of the work space.

In order to provide a maximum amount of viewing coverage or subtended angle, mechanical pan/tilt mechanisms usually use motorized drives and gear mechanisms to manipulate the vertical and horizontal orientation. An example of such a device is shown in U.S. Pat. No. 4,728,839 issued to J. B. Coughlan, et al, on Mar. 1, 1988. Collisions with the working environment caused by these mechanical pan/tilt orientation mechanisms can damage both the camera and the work space and impede the remote handling operation. Simultaneously, viewing in said remote environments is extremely important to the performance of inspection and manipulation activities.

Camera viewing systems that use internal optics to provide wide viewing angles have also been developed in order to minimize the size and volume of the camera and the intrusion into the viewing area. These systems rely on the movement of either a mirror or prism to change the tilt-angle of orientation and provide mechanical rotation of the entire camera to change the pan angle of orientation. Additional lenses are used to minimize distortion. Using this means, the size of the camera orientation system can be minimized, but “blind spots” in the center of the view result. Also, these systems typically have no means of magnifying the image and or producing multiple images from a single camera.

Further, references that may be relevant to the evaluation of the captured image transformations as described herein include U.S. Pat. No. 4,772,942 issued to M. J. Tuck on Sep. 20, 1988; U.S. Pat. No. 5,067,019 issued to R. D. Juday on Nov. 19, 1991; and U.S. Pat. No. 5,068,735 issued to K. Tuchiya, et al on Nov. 26, 1991.

OBJECTS OF THE INVENTION

Accordingly, it is an object of the present invention to provide an apparatus that captures at least one hemispherical image for later manipulation.

Another object of the invention is to provide an apparatus which captures a spherical image from two images produced by two cameras.

Another object of the invention is to form a single spherical image from the captured image or images.

It is a further object of the invention to provide a spherical image capture system and method without the bulk of a large number of cameras and the necessity of multiple camera alignment.

Another object of the invention is to reduce the number of seams in a formed image.

Another object of the invention is to accomplish the above objectives using a single-use, disposable camera.

Another object of the invention is to provide a system for displaying a complete spherical image with perspective correction and without edge effects and image distortion.

Another object of the invention is to enable interaction with any portion of the spherical image with the selected portion being perspective corrected.

It is another object of the present invention to provide horizontal orientation (pan), vertical orientation (tilt) and rotational orientation (rotation) of the viewing direction with no moving mechanisms.

It is another object of the present invention to provide the ability to magnify or scale the image (zoom in and out) electronically.

It is another object of the present invention to provide electronic control of the image intensity (iris level).

It is another object of the present invention to be able to accomplish pan, tilt, zoom, rotation, and iris adjustment with simple inputs made by a lay person from a joystick, keyboard controller, or computer controlled means.

It is also an object of the present invention to provide accurate control of the absolute viewing direction and orientations using said input devices.

A further object of the present invention is to provide the ability to produce multiple images with different orientations and magnifications simultaneously from a single input image.

Another object of the present invention is to be able to provide these images at real-time video rate, e.g. thirty transformed images per second, and to support various display format standards such as the National Television Standards Committee RS-170 signal format and/or higher resolution formats currently under development and to provide the images to a computer display performing perspective correction transforms on a personal computer system.

It is also an object of the present invention to provide a system than can be used for automatic or manual surveillance of selected environments, with optical views of these environments corrected electronically to remove distortion so as to facilitate this surveillance.

It is another object of this invention to provide a means for directly addressing each picture element of an analog image captured with an imaging device having a field-of-view, the picture elements being addressed in a non-linear sequence determined in a manner similar to that described by U.S. Pat. No. 5,185,667 to provide a distortion-corrected image without requiring the use of filters and memory holding buffers.

Another object of the present invention is to provide a means for directly addressing each picture element of an image (still or video) captured using an imaging device having a two-dimensional field-of-view.

SUMMARY OF THE INVENTION

According to the principles of the present invention, at least one camera with a 180° or greater field-of-view lens captures a spherical image. When the system employs two cameras with such lenses, the cameras and lenses are mounted in a back-to-back arrangement. When used in this disclosure and attached claims, “back-to-back” means two cameras clasped together such that the image planes of the lenses fall between each of the lenses and both lenses' optical axes are collinear with a single line which passes through each lens and camera. An imaging element or elements capture the images produced by the lenses. When used herein and in the claims, an “imaging element” or “imaging elements” refer to both film and linear scanning devices and alternatives thereof upon which an image is focused and captured. The captured images from each camera are stored and combined to form a single, spherical image (a final, formed image). When used herein and in the claims, “stored” not only means to digitally store an image in a retrievable form but also means to capture the image on film. To form the spherical image, the system includes a converter which identifies, joins, and smooths the edges (also referred to as the “seams”) of each hemispherical image. When used herein and in the claims, a “converter” refers to not only a manual system (splicing by hand and airbrush image altering techniques) but also an automatic image processing system (digital processing by a computer where images are altered-automatically) for combining the two images together. Where a partial overlap exists between the two hemispherical images, the converter processes the partial overlap to remove the overlap and any distortion and create a single, complete, formed spherical image. Finally, a selected planar portion of the spherical image may be displayed on a personal computer using perspective correction software or hardware.

A method for capturing a spherical image includes the steps of capturing a first hemispherical image with a first camera including a first 180° or greater field-of-view lens; receiving a second hemispherical image either by capturing the second hemispherical image by means of a second camera including a second oppositely directed 180° or greater field-of-view lens or by creating a mirror image of the first hemispherical image; and, combining the first and second oppositely directed hemispherical images to create a spherical image.

An apparatus capturing a spherical image includes a first camera equipped with a 180° or greater field-of-view lens, the first camera and the lens directed in a first direction, the first camera capturing a first image; a second device either forming a second image corresponding to a mirror image of the first image or including a second camera equipped with a 180° or greater field-of-view lens, directed in a second direction opposite to the first direction, the second camera capturing the second image; and, a combining system for combining the first and second images into a formed spherical image.

The cameras disclosed above capture high resolution images. Various cameras may be used including still cameras, video cameras, and CCD, CID, or CMOS APS cameras. With high resolution (crystal clear) images as a goal, the system employs a still camera capturing a high resolution image on a fine grain film. Film generally composes a layer of silver halide crystals. Upon exposure to light, this silver halide layer picks up the image exposed to it. The greater the number of separate halide crystals, the greater the resolution of the film. Thus, a finer grain size refers to an increase in number of silver halide crystals per unit area of film which in turn refers to an increase in the potential resolution of the film medium.

When capturing a spherical image with two single-use cameras, the cameras include additional features allowing for dual image capture. Where “single-use camera” is referred to herein and in the claims, it refers to a disposable camera or other alternative. The additional features which aid in spherical image capture include attachment devices which attach the backs of the cameras to each other. When used herein, “attachment devices” refer to locking pins, locking clasps, lever and hook systems, and alternatives thereof. Also, each camera's shutter release may be controlled by a single button (common shutter release control) with either a mechanical or electrical servo linkage releasing each camera's shutter. Additionally, to allow a photographer to avoid his or her image from being captured by the spherical image capture system, the dual camera system includes a shutter auto timer or a remote shutter activation control controlling the common shutter release control. The remote shutter control may be an IR transmitter or remote shutter release cable. Further, the dual camera system may include two different shutters operable independently or sequentially. The sequential shutter operations allow the photographer to walk around to the other side of the dual camera system so as not to become part of the captured spherical image.

According to the present invention, when using a still image recorded on film, after developing the film, a high resolution digital scanner scans and digitizes the image contained in the developed film and stores the digitized image in a retrievable medium. The retrievable medium includes, inter alia, CD-ROMs, magnetic disks and tapes, semiconductor devices, and magneto-optical disks.

As referred to above, the second image may be created from the first image. This may be accomplished by at least one of two methods: first, manually, by forming the second image by hand and, second, automatically, by means of a computer running image processing software. As to manually creating the image, the film developing and printing steps generate the second image. For example, after printing or scanning the first hemispherical image, a technician or device flips or likewise reverses the film storing the at least hemispherical image (from left to right orientation to right to left orientation) and scans or prints the film again.

The automatic printing or scanning technique creates the second hemispherical image (also known as a mirror image of the first image) through appropriate software. Alternatively, image processing software or hardware may reverse the scanned image without the need to manually flip a developed piece of film.

The converter (automatic or manual) seams the two hemispherical images together and stores a generated, complete spherical image in a storage medium including CD-ROMs, magnetic disks and tapes, semiconductor devices and magneto-optical disks. This converting may be accomplished by sending the camera and/or film to a processing center which sends back the spherical image stored in one of the above storage mediums.

Finally, using the perspective correction and manipulation system as disclosed in U.S. Pat. No. 5,185,667 and its progeny including U.S. Pat. Nos. 5,359,363 and 5,313,306 and Ser. Nos. 08/189,585, 08/339,663, and 08/373,446, the formed, seamless, spherical image may be explored. These patents and applications and others herein are expressly incorporated by reference.

Preferably, a personal computer system runs the perspective correction software or hardware. These computers may be directly linked to the image capturing system (allowing viewing of the spherical image as captured by the hemispherical camera or cameras and manipulated by the perspective correction system) or may remain completely separate (photographing an image, sending the film to a processing center which creates a spherical image from the photograph or photographs, and returning the spherical image stored in a retrievable form for display on a personal computer).

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:

FIG. 1 is a diagram of the fields of view for 180° and greater than 180° fields of view lenses as mounted to a single camera body.

FIG. 2 shows two back-to-back cameras each capturing more than 180° fields of view images.

FIG. 3 shows two back-to-back cameras each capturing 180° fields of view images.

FIG. 4 shows an alternated embodiment of the spherical capture system of the present invention.

FIGS. 5A and 5B relate to the elements used to capture a spherical image.FIG. 5A shows two hemispherical lenses capturing complementary hemispherical images and feeding them to remote cameras.FIG. 5B shows a hemispherical lens capturing a hemispherical image and a mirror image converter for converting the first hemispherical image into a second hemispherical image.

FIG. 6A shows two hemispherical lenses similar to that ofFIG. 5A passing images to local cameras through reflective and refractive optics.FIG. 6B shows two hemispherical lenses conveying images to a single camera.

FIGS. 7A and 7B represent two hemispherical images combined into a single spherical image.

FIG. 8 shows a storage/display option of the instant invention.

FIGS. 9A and 9B show a schematic block diagram of the signal processing portion of the present invention illustrating the major components thereof.FIG. 9A shows the perspective correction process implemented in hardware.FIG. 9B shows the perspective correction process implemented in software, operating inside a personal computer.

FIG. 10 is an exemplary drawing of an at least hemispherical image used as input by the present invention. Lenses having other field-of-view values will produce images with similar distortion, particularly when the field-of-view is about eighty degrees or greater.

FIG. 11 is an exemplary drawing of the output image after correction for a desired image or orientation and magnification within the original image.

FIG. 12 is a schematic diagram of the fundamental geometry that the present invention embodies to accomplish the image transformation.

FIG. 13 is a schematic diagram demonstrating the projection of the object plane and position vector into image plane coordinates.

DETAILED DESCRIPTION OF THE INVENTION

Spherical Image Capture

The disclosed Spherical Image Capture system employs the components disclosed inFIGS. 1-8 to capture hemispherical images and form spherical images. The image transform engine as disclosed inFIGS. 9-13 operates to transform selected portions of the formed spherical images into planar, perspective corrected portions.

Referring toFIG. 1,camera601 includeslens602 with optical axis A, image plane I, and a field-of-view of 180° or greater. Iflens602 has a 180° field-of-view it captures at most the image fromhemisphere603. On the other hand, iflens602 has a field-of-view greater than 180°, then it captures the image from sector604 (shown by dotted lines) as well as that ofhemisphere603.

FIG. 2 shows a camera body701 (which may include two cameras) connected tolenses702 and703 (with image planes I₇₀₂and I₇₀₃, respectively). Each oflenses702 and703 have fields of view greater than 180°. Placed in a back-to-back arrangement where the lenses are mounted such that the image planes I₇₀₂and I₇₀₃from the lenses fall between each of the lenses and both lenses' optical axes A coincide in a single line which passes through each lens and camera, they capture the spherical image surrounding thecamera body701. It should be noted, however, that the thickness of thecamera body701 plays a role in how much of the spherical image surrounding the camera is captured. Specifically, the objects on the sides of the camera may or may not be completely photographed depending on their distances from thecamera body701. For example, if objects are withinboundary704, some of the objects may fall into the camera'sblind spots707 and not be completely photographed. On the other hand, because of the converging angles of lenses' greater than 180° fields of view, objects withinsectors705 will be photographed twice: first, by means of the image captured bylens702 and, second, by means of the image captured bylens703. Decreasing the distances between the lenses reducesblind spots707 of the spherical capture system. In this example, reducing the distance between the lenses means reducing the thickness of thecamera body701. Reducing the camera body thickness can be accomplished, for example, by using smaller imaging and recording elements such as a CCD, CID, or CMOS APS camera as disclosed in U.S. Ser. No. 08/373,446, expressly incorporated herein by reference. Additionally, the distance between image planes I₇₀₂and I₇₀₃oflenses702 and703, respectively, may be reduced to the point where the image planes coincide, further reducing the thickness of the camera body.

FIG. 3 disclosescamera body801, similar to that ofcamera body701, andlenses802 and803 with image planes I₈₀₂and I₈₀₃, respectively, each having a field-of-view of exactly 180°. Lens802 receives the image of hemisphere804 andlens803 receives the image ofhemisphere805. Similar toFIG. 2 above, the lenses attach tocamera body801 in a back-to-back arrangement where the lenses are mounted such that the image planes I₈₀₂and I₈₀₃from the lenses fall between each of the lenses and both lenses' optical axes A coincide in a single line which passes through each lens and camera. As discussed with reference toFIG. 2 above, becausecamera body801 has a thickness (i.e., the distance betweenlenses802 and803 is greater than zero), theimage capture system800 hasblind spots806 on the sides of thecamera body801. These blind spots may be reduced by decreasing the distance betweenlenses802 and803. Here, this means reducing the thickness ofcamera body801. This may be accomplished, inter alia, by reducing the size of the imaging and recording components as discussed above in reference to FIG.2.

Referring now toFIG. 4, twocameras201 and202 equipped withlenses203,204, each having a field-of-view (FOV) greater than 180°, are disclosed in a back-to-back arrangement (the image planes (not shown) falling between each of the lenses and the optical axes of thelenses203 and204 are collinear as designated by line A). Because eachcamera201,202 has a lens (203,204) which has a field-of-view (FOV) greater than 180°, each captures more than the image of a complete hemisphere. By employing two cameras in this arrangement, the camera system captures a complete spherical image. The types of cameras employed are chosen from the group comprising of at least still cameras with loaded film or digital image capture, motion picture cameras with loaded film or digital image capture, the KODAK™ digital image capture system, video, and linear scanning CID, CCD, or CMOS APS camera arrays. The outputs ofcameras201 and202 connect by means of electrical, optical, or electro-optical links215 to hemispherical-to-spherical image converter216. When the captured hemispherical images are stored on film, optical-to-electrical converter215A converts the stored images into a form usable by hemispherical-to-spherical image converter216. Optical-to-electrical converter215A includes a scanning system which scans a photographed image and outputs a high resolution, electronic replica of the photographed image. One converter includes the Kodak™ Photo-CD Rom converter which takes a photograph and converts it into a high resolution digital form which then may be stored on a compact disk. Hemispherical-to-spherical converter216 receives the hemispherical images fromcameras201 and202 (or alternatively, from optical-to-electrical converter215A).

The cameras include additional features allowing for dual image capture. For example, the backs of the cameras are attached to each other viaseparable attachment devices401.Attachment devices401 may be locking pins, locking clasps, lever and clip systems, etc. Also, each camera's shutter release may be controlled by asingle button402A (common shutter release control) with either a mechanical or electrical servo linkage releasing each camera's shutter. Additionally, to allow a photographer to ensure his or her image is not recorded by the spherical image capture system, the dual camera system includes a shutter auto timer or a remoteshutter activation control403 controlling the common shutter release control, allowing the photographer to move to a concealed or non-image-captured position. Theremote shutter control403 may be an IR transmitter or remote shutter release cable. Further, the dual camera system may include two different shuttersrelease control buttons402B operable independently or sequentially. The sequential shutter operations allow the photographer to walk around to the other side of the dual camera system so as not to become part of the captured spherical image.

Next, hemispherical-to-spherical converter216 combines the hemispherical images into a single, complete spherical image. Finally, the edges of the two hemispherical images may be combined to form a seamless spherical image. Removing the seams from the two hemispherical images may be accomplished in a number of ways. For example, the two images may be “airbrushed” together (where any difference between the two images at the periphery of the images are smoothed together. Alternatively, a more complex method of seaming the two images together may include matching related pixels by their luminance and chrominance values and interpolating the corresponding values for interstitial pixels. In the event that a partial overlap exists between the two hemispherical images, the converter processes the spherical image to remove the partial overlap any distortion and creates a single, complete, formed image. The processing may include choosing and displaying one hemisphere over the other, weighted and non-weighted averaging of the overlapping sections, and linear and non-linear approximations creating intermediary images.

FIG. 5A showslenses203 and204 positioned remotely fromcameras201 and202. Here, the image planes I₂₀₃and I₂₀₄fall betweenlenses203 and204 and the optical axes of thelenses203 and204 are collinear as designated by line A. Electrical, optical (including fiber optic lines), or electro-optical links215 connect the images received fromlenses203 and204 to thecameras201 and202. Next, hemispherical-to-spherical image converter216 receives the outputs fromcameras201 and202 and outputs a spherical image as described in relation to FIG.4.

FIG. 5B showssingle lens203 positioned remotely fromcamera201. Electrical, optical (including fiber optic lines), or electro-optical links215 connect the image received fromlens203 to thecamera201. Next,camera201 captures a first hemispherical image. The output of camera201 (a still or video image contained in a frame or frames of film, digital or analog signal) is sent tomirror image converter901 and one input of the hemispherical tospherical image converter216. Themirror image converter901 assumes many forms depending on the form of image relayed to it. For developed film,converter901 refers to a re-scanning system re-scanning the developed film with the film flipped (flipped from a left to right orientation to a right to left orientation). For an optical or electrical signal,converter901 refers to a signal processing system which automatically creates a second hemispherical image from the first hemispherical image. The output ofconverter901 flows to the hemispherical-to-spherical image converter216 as the second hemispherical image. Finally, hemispherical-to-spherical image converter216 outputs a spherical image as described in relation to FIG.4.

FIG. 6A shows an alternative arrangement of thecameras201 and202 and thelenses203 and204. The optical axes of thelenses203 and204 are collinear as designated by line A. Here, the devices used to convey the images fromlenses203 and204 tocameras201 and202 include hollow chambers withreflective optics215B andrefractive optics215C, as necessary for proper transmission of the hemispherical images. Thereflective optics215B allow thecameras201 and202 to be moved from a location directly behind eachlens203,204. Therefractive optics215C aid in focusing the hemispherical images generated bylenses203 and204. This movement of the cameras from behind the lenses allows the lenses to be moved closer together, maximizing the area photographed.

A further modification includes the substitution of the APS camera array of co-pending U.S. application Ser. No. 08/373,446 (expressly incorporated herein by reference) for the optical system described above. Because of the small size of an APS camera array, two arrays may be placed back to back to further maximize the content of each hemispherical image. An advantage of using APS camera arrays is the shifted processing location of the Omniview engine. Specifically, by adding additional processing circuitry on the APS camera array chip, the selection and “dewarping” transformations may be performed locally on the APS chip. This results in less subsequent processing of the image as well as a reduction in the bandwidth required for sending each hemispherical image to an external processing device.

Furthermore, as described above,image conduits215 may include optical fibers instead of thereflective optics215B andrefractive optics215C. An imaging system including optical fibers connected between a hemispherical lens and imaging array is found in U.S. Pat. No. 5,313,306 to Martin which is expressly incorporated by reference. The present invention includes the application of the spherical imaging system with a combination of an endoscope and dual hemispherical lenses to capture hemispherical images of remote locations.Converter216 combines the hemispherical images to a form complete, spherical image.

FIG. 6B relates to another embodiment where asingle camera201A captures the images produced bylenses203 and204. The optical axes of thelenses203 and204 are collinear as designated by line A. Here, employing a single camera to capture both hemispherical images (fromlenses203 and204) eliminates the bulk of the second camera. For example, wherecamera201A is a still camera, the camera records the two hemispherical images in a single frame in a side-by-side relationship, exposed at the same time or during related time intervals. Alternatively, the two images may be captured in separate frames, exposed at the same time or during related time intervals. The same applies to video and motion picture cameras as well. Image capture with a single camera may be used in the other embodiments of described in greater detail herein. A system ofFIG. 6B including an APS camera array may be mounted onto a single, silicon chip. This combination has multiple advantages including reduced size of the image capture system, reduced bulk from extra cameras, higher resolution from the APS camera arrays.

FIG. 7A shows first205 and second206 hemispherical images, each taken from one ofcameras201 or202.FIG. 7A also shows theedges207,208 (or seams) of each hemispherical image.FIG. 7B shows the twoimages205 and206 combined into a single,spherical image209.Seams207 and208 have been combined to form the single,seamless image209.

FIG. 8 shows a possible future viewing system for viewing the formed spherical image system. The image planes1203 and1204 fall betweenlenses203 and204 and the optical axes of thelenses203 and204 are collinear as designated by line A.Image input buffer217 temporarily stores images received fromcameras201 and202 until hemispherical-to-spherical image converter216 accepts the stored images. Also,FIG. 8 includes options for the spherical images. For example, after combining the two hemispherical images into a single, spherical image inconverter216, the spherical image may be immediately viewed throughviewing engine218.Viewing engine218 includes the Omniview calculation engine with viewer communication interface124 as shown inFIG. 1 of co-pending U.S. Ser. No. 08/373,446 (expressly incorporated herein by reference). Here, the user may view selected portions of the formed spherical image as output from the hemispherical-to-spherical image converter216. Alternatively, the spherical image may be stored instorage device219. The storage device119 may include video tape, CD-ROM, semiconductor devices, magnetic or magneto-optical disks, or laser disks as the storage medium. By the interconnections betweenviewing engine218 andstorage device219, a new spherical image may be displayed and saved instorage device219 as well as saved instorage device219 and viewed at a later time.

Further enhancements include using two side-by-side hemispherical lens equipped cameras for stereo-optical viewing. Additionally, the back-to-back camera system described herein may be attached to the exterior of any of a number of different vehicles for spherical image capture of a number of different environments.

Captured Image Transformation

FIGS. 9-13 relate to the captured image transformation system.

In order to minimize the size of the camera orientation system while maintaining the ability to zoom, a camera orientation system that utilizes electronic image transformation rather than mechanisms was developed. While numerous patents on mechanical pan-and-tilt systems have been filed, no approach using strictly electronic transforms and 180° or greater field of view optics is known to have been successfully implemented. In addition, the electro-optical approach utilized in the present invention allows multiple images to be extracted from the output of a signaled camera. These images can be then utilized to energize appropriate alarms, for example, as a specific application of the basic image transformation in connection with a surveillance system. As utilized herein, the term “surveillance” has a wide range including, but not limited to, determining ingress or egress from a selected environment. Further, the term “wide angle” as used herein means a field-of-view of about eighty degrees or greater. Motivation for this device came from viewing system requirements in remote handling applications where the operating envelop of the equipment is a significant constraint to task accomplishment.

The principles of the optical transform utilized in the present invention can be understood by reference to thesystem10 ofFIGS. 9A and 9B. (This is also set forth in the aforecited U.S. patent application Ser. No. 07/699,366 that is incorporated herein by reference.) Referring toFIG. 9A, shown schematically at11 is a wide angle, e.g., a hemispherical, lens that provides an image of the environment with a 180 degree or greater field-of-view. The lens is attached to acamera12 which converts the optical image into an electrical signal. These signals are then digitized electronically13 and stored in animage buffer14 within the present invention. An image processing system consisting of an X-MAP and a Y-MAP processor shown as16 and17, respectively, performs the two-dimensional transform mapping. The image transform processors are controlled by the microcomputer andcontrol interface15. The microcomputer control interface provides initialization and transform parameter calculation for the system. The control interface also determines the desired transformation coefficients based on orientation angle, magnification, rotation, and light sensitivity input from an input means such as ajoystick controller22 or computer input means23. The transformed image is filtered by a 2-dimensional convolution filter18 and the output of the filtered image is stored in anoutput image buffer19. Theoutput image buffer19 is scanned out bydisplay electronics20 to avideo display device21 for viewing.

A range of lens types can be accommodated to support various fields of view. Thelens optics11 correspond directly with the mathematical coefficients used with the X-MAP and Y-MAP processors16 and17 to transform the image. The capability to pan and tilt the output image remains even though a different maximum field-of-view is provided with a different lens element.

The invention can be realized by proper combination of a number of optical and electronic devices. Thelens11 is exemplified by any of a series of wide angle lenses from, for example, Nikon, particularly the 8 mm F2.8. Anyvideo source12 andimage capturing device13 that converts the optical image into electronic memory can serve as the input for the invention such as a Videk Digital Camera interfaced with Texas Instrument's TMS 34061 integrated circuits. Input and output image buffers14 and19 can be construed using Texas Instrument TMS44C251 video random access memory chips or their equivalents. The control interface can be accomplished with any of a number of microcontrollers including the Intel 80C196. The X-MAP and Y-MAP transform processors16 and17 andimage filtering19 can be accomplished with application specific integrated circuits or other means as will be known to persons skilled in the art. The display driver can also be accomplished with integrated circuits such as the Texas Instruments TMS34061. The output video signal can be of the NTSC RS-170, for example, compatible with most commercial television displays in the United States.Remote control22 andcomputer control23 are accomplished via readily available switches and/or computer systems than also will be well known. These components function as a system to select a portion of the input image (hemispherical or other wide angle) and then mathematically transform the image to provide the proper prospective for output. The keys to the success of the perspective correction system include:

• • (1) the entire input image need not be transformed, only the portion of interest;
  • (2) the required mathematical transform is predictable based on the lens characteristics; and
  • (3) calibration coefficients can be modified by the end user to correct for any lens/camera combination supporting both new and retrofit applications.

FIG. 9B contains elements similar to that ofFIG. 9A but is implemented in a personal computer represented by dashed line D. The personal computer includescentral processing unit15′ performing the perspective correction algorithms X-MAP16′ and Y-MAP17′ as stored in RAM, ROM, or some other form. Thedisplay driver20 outputs the perspective corrected image to computer display monitor21′.

The transformation that occurs between theinput memory buffer14 and theoutput memory buffer19, as controlled by the two coordinatedbuffer19, as controlled by the two coordinatedtransformation circuits16 and17 ofFIG. 9A (or algorithms as stored in16′ and17′ of FIG.9B), is better understood by referring toFIG. 10 is a rendering of the image of a grid pattern produced by a hemispherical lens. This image has a field-of-view of 180 degrees and shows the contents of the environment throughout and entire hemisphere. Notice that the resulting image inFIG. 10 is significantly distorted relative to human perception. Similar distortion will be obtained even with lesser field-of-view lenses. Vertical grid lines in the environment appear in the image plane as24a,24b, and24c. Horizontal grid lines in the environment appear in the image plane as25a,25b, and25c. The image of an object is exemplified by26. A portion of the image inFIG. 10 has been corrected, magnified, and rotated to produce the image shown in FIG.11.Item27 shows the corrected representation of the object in the output display. The results shown in the image inFIG. 11 can be produced from any portion of the image ofFIG. 10 using the present invention. The corrected perspective of the view is demonstrated by the straightening of the grid pattern displayed in FIG.11. In the present invention, these transformations can be performed at real-time video rates (e.g., thirty times per second), compatible with commercial video standards.

The transformation portion of the invention as described has the capability to pan and tilt the output image through the entire field-of-view of the lens element by changing the input means, e.g. the joystick or computer, to the controller. This allows a large area to be scanned for information as can be useful in security and surveillance applications. The image can also be rotated through any portion of 360 degrees on its axis changing the perceived vertical of the displayed image. This capability provides the ability to align the vertical image with the gravity vector to maintain a proper perspective in the image display regardless of the pan or tilt angle of the image. The invention also supports modifications in the magnification. used to display the output image. This is commensurate with a zoom function that allows a change in the field-of-view of the output image. This function is extremely useful for inspection and surveillance operations. The magnitude of zoom provided is a function of the resolution of the input camera, the resolution of the output display, the clarity of the output display, and the amount of picture element (pixel) averaging that is used in a given display. The invention supports all of these functions to provide capabilities associated with traditional mechanical pan (through 180 degrees), tilt (through 180 degrees), rotation (through 360 degrees), and zoom devices. The digital system also supports image intensity scaling that emulates the functionality of a mechanical iris by shifting the intensity of the displayed image based on commands from the user or an external computer.

The postulates and equations that follow are based on the image transformation portion of the present invention utilizing a wide angle lens as the optical element. These also apply to other field-of-view lens systems. There are two basic properties and two basic postulates that describe the perfect wide angle lens system. The first property of such a lens is that the lens has a 2π steradian filed-of-view and the image it produces is a circle. The second property is that all objects in the field-of-view are in focus, i.e. the perfect wide angle lens has an infinite depth-of-field. The two important postulates of this lens system (refer toFIGS. 12 and 13) are stated as follows:

Postulate 1: Azimuth angle invariability—For object points that lie in a content plane that is perpendicular to the image plane and passes through the image plane origin, all such points are mapped as image points onto the line of intersection between the image plane and the content plane, i.e. along a radial line. The azimuth angle of the image points is therefore invariant to elevation and object distance changes within the content plane.

Postulate 2: Equidistant Projection Rule—The radial distance, r, from the image plane origin along the azimuth angle containing the projection of the object point is linearly proportional to the zenith angle β, where β is defined as the angle between a perpendicular line through the image plane origin and the line from the image plane origin to the object point. Thus the relationship:
r=kβ  (1)

Using these properties and postulates as the foundation of the lens system, the mathematical transformation for obtaining a perspective corrected image can be determined.FIG. 12 shows the coordinate reference frames for the object plane and the image plane. The coordinates u,v describe object points within the object plane. The coordinates x,y,z describe points within the image coordinate frame of reference.

The object plane shown inFIG. 12 is a typical region of interest to determine the mapping relationship onto the image plane to properly correct the object. The direction of view vector, DOV[x,y,z], determines the zenith and azimuth angles for mapping the object plane, UV, onto the image plane, XY. The object plane is defined to be perpendicular to the vector, DOV[x,y,z].

The location of the origin of the object plane in terms of the image plane [x,y,z] in spherical coordinates is given by:
x=Dsin β cos ∂
y=Dsin β cos ∂
z=Dcos β  (2)
where D=scaler length from the image plane origin to the object plane origin, β is the zenith angle, and ∂ is the azimuth angle in image plane spherical coordinates. The origin of object plane is represented as a vector using the components given inEquation 1 as:
DOV[x,y,z]=[Dsin β cos ∂,Dsin β sin ∂,Dcos β]  (3)

DOV[x,y,z] is perpendicular to the object plane and its scaler magnitude D provides the distance to the object plane. By aligning the XY plane with the direction of action of DOV[x,y,z], the azimuth angle ∂ becomes either 90 or 270 degrees and therefore the x component becomes zero resulting in the DOV[x,y,z] coordinates:
DOV[x,y,z]=[0, −Dsin β,Dcos β]  (4)

Referring now toFIG. 13, the object point relative to the UV plane origin in coordinates relative to the origin of the image plane is given by the following:
x=u
y=vcos β
z=vsin β  (5)
therefore, the coordinates of a point P(u,v) that lies in the object plane can be represented as a vector P[x,y,z] in image plane coordinates:
P[x,y,z]=[u, vcos β,vsin β]  (6)
where P[x,y,z] describes the position of the object point in image coordinates relative to the origin of the UV plane. The object vector o[x,y,z] that describes the object point in image coordinates is then given by:
O[x,y,z]=DOV[x,y,z]+P[x,y,z]  (7)
O[x,y,z]=[u, vcos β−Dsin β,vsin β+Dcos β]  (8)
Projection onto a hemisphere of radius R attached to the image plane is determined by scaling the object vector o[x,y,z] to produce a surface vector s[x,y,z]:$\begin{array}{cc}S\left[x,y,z\right]=\frac{\mathrm{RO}\left[x,y,z\right]}{O\left[x,y,z\right]}& \left(9\right)\end{array}$

By substituting for the components of o[x,y,z] fromEquation 8, the vector S[x,y,z] describing the image point mapping onto the hemisphere becomes:$\begin{array}{cc}S\left[x,y,z\right]=\frac{\mathrm{RO}\left[u,\left(v\cos \beta -D\sin \beta \right),\left(v\sin \beta +D\cos \beta \right)\right]}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\left(v\cos \beta -D\sin \beta \right)}^2+{\left(v\sin \beta +D\cos \beta \right)}^2}}& \left(10\right)\end{array}$

The denominator inEquation 10 represents the length or absolute value of the vector o[x,y,z] and can be simplified through algebraic and trigonometric manipulation to give:$\begin{array}{cc}S\left[x,y,z\right]=\frac{\mathrm{RO}\left[u,\left(v\cos \beta -D\sin \beta \right),\left(v\sin \beta +D\cos \beta \right)\right]}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\mathrm{<figure-callout\; label="v"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">v</figure-callout>}}^2+D^2}}& \left(11\right)\end{array}$

FromEquation 11, the mapping onto the two-dimensional image plane can be obtained for both x and y as:$\begin{array}{cc}x=\frac{\mathrm{<figure-callout\; label="Ru\; u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">Ru</figure-callout>}}{\sqrt{u^{}}}& \left(12\right)\\ y=\frac{R\left(v\cos \beta -D\sin \beta \right)}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\mathrm{<figure-callout\; label="v"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">v</figure-callout>}}^2+D^2}}& \left(13\right)\end{array}$

Additionally, the image plane center to object plane distance D can be represented in terms of the image circular radius R by the relation:
D=mR  (14)

• • where m represents the scale factor in radial units R from the image plane origin to the object plane origin. SubstitutingEquation 14 intoEquations 12 and 13 provides a means for obtaining an effective scaling operation or magnification which can be used to provide zoom operation.$\begin{array}{cc}x=\frac{\mathrm{<figure-callout\; label="Ru\; u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">Ru</figure-callout>}}{\sqrt{u^{}}}& \left(15\right)\\ y=\frac{R\left(v\cos \beta -\mathrm{mR}\sin \beta \right)}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\mathrm{<figure-callout\; label="v"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">v</figure-callout>}}^2+{\mathrm{<figure-callout\; label="m"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">m</figure-callout>}}^2{R}^2}}& \left(16\right)\end{array}$

Using the equations for two-dimensional rotation of axes for both the UV object plane and the XY image plane the last two equations can be further manipulated to provide a more general set of equations that provides for rotation within the image plane and rotation within the object plane.$\begin{array}{cc}x=\frac{R\left[\mathrm{uA}-\mathrm{vB}+\mathrm{mR}\sin \beta \sin \partial \right]}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\mathrm{<figure-callout\; label="v"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">v</figure-callout>}}^2+{\mathrm{<figure-callout\; label="m"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">m</figure-callout>}}^2{R}^2}}& \left(17\right)\\ y=\frac{R\left(\mathrm{uC}-\mathrm{vD}-\mathrm{mR}\sin \beta \cos \partial \right)}{\sqrt{{\mathrm{<figure-callout\; label="u"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">u</figure-callout>}}^2+{\mathrm{<figure-callout\; label="v"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">v</figure-callout>}}^2+{\mathrm{<figure-callout\; label="m"\; filenames="US7382399-drawings-page-10.png,US7382399-drawings-page-7.png"\; state="\{\{state\}\}">m</figure-callout>}}^2{R}^2}}& \left(18\right)\end{array}$

• • where:
    A=(cos ø cos ∂−sin ø sin ∂ cos β)
    B=(sin ø cos ∂+cos ø sin ∂ cos β)
    C=(cos ø sin ∂+sin ø cos ∂ cos β)
    D=(sin ø sin ∂−cos ø cos ∂ cos β)  (19)
  • and where:
  • R=radius of the image circle
  • β=zenith angle
  • ∂=Azimuth angle in image plane
  • ø=Object plane rotation angle
  • m=Magnification
  • u,v=object plane coordinates
  • x,y=image plane coordinates

TheEquations 17 and 18 provide a direct mapping from the UV space to the XY image space and are the fundamental mathematical result that supports the functioning of the present omnidirectional viewing system with no moving parts. By knowing the desired zenith, azimuth, and object plane rotation angles and the magnification, the locations of x and y in the imaging array can be determined. This approach provides a means to transform an image from the input video buffer to the output video buffer exactly. Also, the image system is completely symmetrical about the zenith, therefore, the vector assignments and resulting signs of various components can be chosen differently depending on the desired orientation of the object plane with respect to the image plane. In addition, these postulates and mathematical equations can be modified for various lens elements as necessary for the desired field-of-view coverage in a given application.

The input means defines the zenith angle, β, the azimuth angle, ∂, the object rotation, ø, and the magnification, m. These values are substituted intoEquations 19 to determine values for substitution intoEquations 17 and 18. The image circle radius, R, is fixed value that is determined by the camera lens and element relationship. The variables u and v vary throughout the object plane determining the values for x and y in the image plane coordinates.

From the foregoing, it can be seen that a wide angle lens provides a substantially hemispherical view that is captured by a camera. The image is then transformed into a corrected image at a desired pan, tilt, magnification, rotation, and focus based on the desired view as described by a control input. The image is then output to a television display with the perspective corrected. Accordingly, no mechanical devices are required to attain this extensive analysis and presentation of the view of an environment through 180 degrees of pan, 180 degrees of tilt, 360 degrees of rotation, and various degrees of zoom magnification.

As indicated above, one application for the perspective correction of images obtained with a motionless wide angle camera is in the field of surveillance. The term “surveillance” is meant to include inspection and like operations as well. It is often desired to continuously or periodically view a selected environment to determine activity in that environment. The term “environment” is meant to include such areas as rooms, warehouses, parks and the like. This activity might be, for example, ingress and egress of some object relative to that environment. It might also be some action that is taking place in that environment. It may be desired to carry out this surveillance either automatically at the desired frequency (or continuously), or upon demand by an operator. The size of the environment may require more than one motionless camera for complete surveillance.

While a preferred embodiment has been shown and described, it will be understood that it is not intended to limit the disclosure, but rather it is intended to cover all modifications and alternate methods falling within the spirit and the scope of the invention as defined in the appended claims. All of the above referenced U.S. patents and pending applications referenced herein are expressly incorporated by reference.

Having thus described the aforementioned invention,

Claims (38)

1. A system for providing perspective corrected views of a selected portion of a received optical image captured using a wide angle lens, the received optical image being distorted, the system comprising:

image capture means for receiving signals corresponding to said received optical image and for digitising said signal;

input image memory means for receiving said digitised signal;

input means for selecting a non-predetermined portion of said received image to view;

image transform processor means for processing said digitised signals to produce an output signal corresponding to a perspective corrected image of said selected portion of said received image;

output image memory means for receiving said output signal from said image transform processor means; and

output means connected to said output image memory means for recording or displaying said perspective corrected image of said selected portion;

characterised in that said image transform processor means comprises transform parameter calculation means for calculating transform parameters in response to the selection of said selected portion of said image and processes said digitised signal based on said calculated transform parameters to generate said output signal.

2. A system according toclaim 1, comprising a camera imaging system for receiving said optical image and for producing said signals corresponding to said received optical image for output to said image capture means.

3. A system according toclaim 2, comprising wide angle lens means mounted on said camera imaging system for producing said optical image for optical conveyance to said camera imaging system.

4. A system according toclaim 3, wherein said lens means is one or more fish-eye lenses.

5. A system according toclaim 1, wherein said input means provides for input to said image transform processor means of one or more of: a direction of view; tilting of a viewing angle; rotation of a viewing angle; pan of said viewing angle; focus of said image and magnification of the selected portion of the image.

6. A system according toclaim 5, wherein tilting of said viewing angle through at least 180 degrees is provided for.

7. A system according toclaim 4, wherein rotation of said viewing angle through 360 degrees is provided for.

8. A system according to any one of claims5, wherein pan of said viewing angle through at least 180 degrees is provided for.

9. A system according toclaim 8, wherein pan of said viewing angle through 360 degrees is provided for.

10. A system according toclaim 1, wherein said input means is a user-operated manipulator switch means.

11. A system according to any one of claims1, wherein said input means is a signal from a computer input means.

12. A system according toclaim 1, wherein said image transform processing means is programmed to implement the following two equations:$x=\frac{R\left\{\mathrm{uA}-\mathrm{vB}+\mathrm{mR}\sin \beta \sin \delta \right\}}{\sqrt{u^2+v^2+m^2{R}^2}}$$y=\frac{R\left\{\mathrm{uC}-\mathrm{vD}+\mathrm{mR}\sin \beta \sin \delta \right\}}{\sqrt{u^2+v^2+m^2{R}^2}}$

where:

A=(cos φ cos δ−sin φ sin δ cos β)

B=(sin φ cos δ+cos φ sin δ cos β)

C=(cos φ sin δ+sin φ cos δ cos β)

D=(sin φ sin δ+cos φ cos δ cos β)

and where:

R=radius of the image circle

β=zenith angle

δ=Azimuth angle in image plane

φ=Object plane rotation angle

m=Magnification

u,v=object plane coordinates

x,y=image plane coordinates.

13. A method for providing perspective corrected views of a selected portion of an optical image captured with a wide angle lens, the received optical image being distorted, the method comprising:

providing a digitised signal corresponding to said optical image;

selecting a non-predetermined portion of said optical image;

transforming said digitised signal to produce an output signal corresponding to a perspective corrected image of said selected portion of said received image; and

displaying or recording said perspective corrected image of said selected portion;

characterised in that said step of transforming said digitised signal comprises calculating transform parameters in response to the selection of said selected portion of said image, said calculated transform parameters being used to control said transformation of the digitised signal to generate said output signal.

14. A method according toclaim 13, comprising first receiving said optical image, producing signals corresponding to said received optical image and digitizing said signals.

15. A method according toclaim 13, comprising capturing said optical image with one or more fish-eye lenses.

16. A method according to any one of claims13, wherein said step of selecting the portion of the image to view comprises selecting one or more of: a direction of view; tilting of a viewing angle; rotation of a viewing angle; pan of said viewing angle; focus of said image and magnification of the selected portion of the image.

17. A method according toclaim 16, wherein tilting of said viewing angle through at least 180 degrees is provided for.

18. A method according toclaim 16, wherein rotation of said viewing angle through 360 degrees is provided for.

19. A method according to any one of claims16, wherein pan of said viewing angle through at least 180 degrees is provided for.

20. A method according toclaim 19, wherein pan of said viewing angle through 360 degrees is provided for.

21. A method according to any one of claims13, wherein selection of said portion of the image to view is achieved using a user-operated manipulator switch means.

22. A method according to any one of claims13, wherein selection of said portion of the image to view is controlled by a signal from a computer input means.

23. A method according to any one of claims13, wherein said image transformation implements the following two equations:$x=\frac{R\left\{\mathrm{uA}-\mathrm{vB}+\mathrm{mR}\sin \beta \sin \delta \right\}}{\sqrt{u^2+v^2+m^2{R}^2}}$$y=\frac{R\left\{\mathrm{uC}-\mathrm{vD}+\mathrm{mR}\sin \beta \sin \delta \right\}}{\sqrt{u^2+v^2+m^2{R}^2}}$

where:

A=(cos φ cos δ−sin φ sin δ cos β)

B=(sin φ cos δ+cos φ sin δ cos β)

C=(cos φ sin δ+sin φ cos δ cos β)

D=(sin φ sin δ+cos φ cos δ cos β)

and where:

R=radius of the image circle

β=zenith angle

δ Azimuth angle in image plane

φ=Object plane rotation angle

m=Magnification

u,v=object plane coordinates

x,y=image plane coordinates.

24. A method according to any one of claims13, wherein a plurality of portions of said image are selected for viewing and are displayed either simultaneously or consecutively.

25. A method according to any one of claims13, wherein the image is viewed interactively by repeating the steps of selecting, transforming and displaying said portion of the image.

26. A method according toclaim 13, wherein said step of transforming the image is based on lens characteristics of the wide angle lens.

27. A method according toclaim 26, wherein the step of transformation is based on azimuth angle invariability and equidistant projection.

28. A method according toclaim 13, wherein the step of transforming the image is performed at real time video rates.

29. A method for providing perspective corrected views of a selected portion of a spherical image comprising two images captured with a fisheye lens, the received spherical image being distorted, the method comprising:

providing a digitised signal corresponding to said spherical image;

selecting a portion of said spherical image;

transforming said digitised signal to produce an output signal corresponding to a perspective corrected image of said selected portion of said spherical image; and

displaying or recording said perspective corrected image of said selected portion;

characterised in that said step of transforming said digitised signal comprises calculating transform parameters for said selected portion of said image, said calculated transform parameters being used to control said transformation of the digitised signal to generate said output signal.

30. A system for providing perspective corrected views of a selected poriton of a received optical image captured using a wide angle lens, the received optical image being distorted, the system comprising:

image capture means for receiving signals corresponding to said received optical image and for digitizing said signal;

input image memory means for receiving said digitized signal;

input means for selecting a portion of said received image to view;

image transform processor means for processing said digitized signals to produce an output signal corresponding to a perspective corrected image of said selected portion of said received image;

output image memory means for receiving said output signal from said image transform processor means; and

output means connected to said output image memory means for recording or displaying said perspective corrected image of said selected portion;

characterized in that the input means is adapted to input a pan, tilt and magnification for the selected portion; and said image transform processor means comprises transform parameter calculation means for calculating transform parameters in response to the input pan, tilt and magnification for the selected portion of said image and processes said digitized signal based on said calculated transform paraeters to generate said output signal.

31. A method for providing perspective corrected views of a selected portion of an optical image captured with a wide angle lens, the received optical image being distorted, the method comprising:

providing a digitized signal corresponding to said optical image;

selecting a portion of said optical image; transforming said digitized signal to produce an output signal corresponding to a perspective corrected image of said selected portion of said received image; and

displaying or recording said perspective corrected of said selected portion;

characterized in that the step of selecting the portion inputting a pan, tilt and magnification; and said step of transforming said digitized signal comprises calculating transform parameters in response to the input pan, tilt and magnification for the selected portion of said image, said calculated transform parameters being used to control said transformation of the digitized signal to generate said output signal.

32. A method of processing images, comprising:

(a) capturing a wide-angle image from a motionless lens, the wide-angle image being distorted relative to human perception;

(b) creating a digitized image corresponding to the captured wide-angle image;

(c) receiving incremental inputs corresponding to pan, tilt, and magnificatio;

(d) defining a portion of the digitized image with motionless pan, tilt, and magnification;

(e) transforming the portion of the digitized wide-angle image to remove the distortion in real-time relative to the received incremental inputs corresponding to pan, tilt, and magnification; and

(f) displaying the transformed portion.

33. The method ofclaim 32, wherein the step of displaying is performed at video rates.

34. The method ofclaim 32, wherein the wide-angle image is captured with a fisheye lens.

35. The method ofclaim 32, wherein the act of removing the distortion comprises direct mapping from a2-D image plane to a2-D object plane.

36. The method ofclaim 32, further comprising displaying multiple undistorted portions with different orientations simultaneously.

37. The method ofclaim 32, wherein the wide-angle image is hemispherical.

38. The method ofclaim 32, wherein the wide-angle image is sphereical.

Images